Several plant pathogenic and/or post-harvest Fusarium species on cereals produce toxic substances of considerable concern to livestock and poultry producers, e.g., deoxynivalenol, T-2 toxin, HT-2 toxin, diacetoxyscirpenol and zearalenone.
Zearalenone is found worldwide in a number of cereal crops, such as maize, barley, oats, wheat, rye, rice, millet and sorghum. Zearalenone production does not seem to occur in significant amounts prior to harvest, but under proper environmental conditions, it is readily produced on corn and small grains in storage.
When cereal grain is used in ethanol production and the starch is consumed the zearalenone is concentrated in the fermentation by-products, e.g., in the distiller's dried grain. The contents of zearalenone in the fermentation by-products may be increased three-fold relative to the cereal grain.
The toxin is heat-stable, and it is not destroyed by long storage, roasting, or by the addition of propionic acid or mold retardants.
Despite their structural dissimilarity to the steriodal estrogens, zearalenone and several of its derivatives possess estrogenic activity. Zearalenone undergoes a folding such that hydroxyl or potential hydroxyl groups become appropriately orientated to facilitate binding to tissue receptors that normally bind estrogens.
Zearalenone is the primary toxin causing infertility, abortion or other breeding problems, especially in swine. The symptoms are especially severe in prepubertal gilts including enlarged mammae, swelling of uterus and vulva, and atrophy of the ovaries. In severe cases, prolapse of the vulva and rectum may occur. Boars exhibit enlarged mammae and atrophied testes.
Zearalenone is present in the meat from animals feeding on contaminated grain as well as in bread baked from contaminated wheat. While cases of poisoning of humans are rare there is concern about the effect of the long term exposure of humans to such an estrogenic activity.
Inactivation of mycotoxins, including zearalenone, using epoxidase or lactonase is disclosed in WO 96/12414.
There is a need for further methods of detoxification of animal feed products, e.g., such as fermentation by-products, including distiller's wet and dried grain, contaminated by the mycotoxin zearalenone.